Question

Difficulty: MediumGas Laws and the Ideal Gas Equation

A heavy-duty truck tire contains a fixed mass of air at an initial absolute pressure of 2.00×105 Pa2.00 \times 10^5\text{ Pa} and a temperature of 27C27^\circ\text{C}. After traveling a long distance, friction causes the temperature of the air inside the tire to increase to 57C57^\circ\text{C} while its volume remains constant. What is the new absolute pressure of the air inside the tire in pascals (Pa\text{Pa})?

Answer: 220000 Pa

Answer

The new absolute pressure of the air inside the tire is 220,000 Pa220,000\text{ Pa} (or 2.20×105 Pa2.20 \times 10^5\text{ Pa}).
According to Gay-Lussac's Law, at constant volume, pressure is directly proportional to absolute temperature (PTP \propto T). Converting temperatures to Kelvin gives T1=300 KT_1 = 300\text{ K} and T2=330 KT_2 = 330\text{ K}. Calculating P2=P1×T2T1P_2 = P_1 \times \frac{T_2}{T_1} gives 2.00×105 Pa×330300=220,000 Pa2.00 \times 10^5\text{ Pa} \times \frac{330}{300} = 220,000\text{ Pa}.

Step-by-Step Solution

1
Convert the initial and final temperatures from Celsius to the absolute Kelvin scale.
T1=27C+273=300 KT_1 = 27^\circ\text{C} + 273 = 300\text{ K} and T2=57C+273=330 KT_2 = 57^\circ\text{C} + 273 = 330\text{ K}.
All gas law equations require absolute temperatures in Kelvin.
2
Apply the Pressure Law (Gay-Lussac's Law) for a fixed volume of gas.
P1T1=P2T2\frac{P_1}{T_1} = \frac{P_2}{T_2}
When volume is constant, gas pressure is directly proportional to absolute temperature.
3
Substitute the known values into the equation to calculate the final pressure P2P_2.
P2=2.00×105 Pa×330 K300 K=2.20×105 Pa=220,000 PaP_2 = 2.00 \times 10^5\text{ Pa} \times \frac{330\text{ K}}{300\text{ K}} = 2.20 \times 10^5\text{ Pa} = 220,000\text{ Pa}.
Multiplying the initial pressure by the ratio of absolute temperatures gives the new pressure.

Key Concept

Pressure Law (Gay-Lussac's Law)
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